<?php
function  sub($a, $b){
  return $a-$b;
}
$a = 200;
$b = 10;
$result = sub($a,$b);
echo $result;
?>
<form action="" mothod="post">
<input type="text" value="<?php echo $a; ?>" name="a"/>-<input type="text" name="b" value="<?php echo $b; ?>"/>=<?php echo $result; ?><br/>
<input type="submit"/>
 </form>
 <?php
 function  avm($a, $b){
   return $a*$b;
 }
 $a = 100;
 $b = 50;
 $result = sub($a,$b);
 echo $result;
 ?>
 <form action="" mothod="post">
 <input type="text" value="111" name="a"/>*<input type="text" name="b" value="3"/>=333<br/>
 <input type="submit"/>
  </form>
